Fibre treatment method

ABSTRACT

The fibrillation tendency of solvent-spun cellulose fibre is reduced by treating the fibre with a cross-linking agent and a flexible linear polymer with terminal functional groups, for example polyethylene glycol (PEG) of molecular weight 300 to 600. The fibre may be treated in never-dried or in fabric form.

FIELD OF THE INVENTION

This application is a 371 of PCT/GB94/00461 filed Mar. 9, 1994 andpublished as WO94/20656 Sep. 15, 1994.

This invention is concerned with a method of reducing the fibrillationtendency of solvent-spun cellulose fibre.

BACKGROUND ART

It is known that cellulose fibre can be made by extrusion of a solutionof cellulose in a suitable solvent into a coagulating bath. One exampleof such a process is described in U.S. Pat. No 4,246,221, the contentsof which are incorporated herein by way of reference. Cellulose isdissolved in a solvent such as a tertiary amine N-oxide, for exampleN-methylmorpholine N-oxide. The resulting solution is extruded through asuitable die to produce filaments, which are coagulated, washed in waterto remove the solvent and dried. The filaments are generally cut intoshort lengths at some stage after coagulation to form staple fibre. Thisprocess of extrusion and coagulation is referred to as"solvent-spinning", and the cellulose fibre produced thereby is referredto as "solvent-spun" cellulose fibre. It is also known that cellulosefibre can be made by extrusion of a solution of a cellulose derivativeinto a regenerating and coagulating bath. One example of such a processis the viscose process, in which the cellulose derivative is cellulosexanthate. Both such types of process are examples of wet-spinningprocesses. Solvent-spinning has a number of advantages over other knownprocesses for the manufacture of cellulose fibre such as the viscoseprocess, for example reduced environmental emissions.

Fibre may exhibit a tendency to fibrillate, particularly when subjectedto mechanical stress in the wet state. Fibrillation occurs when fibrestructure breaks down in the longitudinal direction so that fine fibrilsbecome partially detached from the fibre, giving a hairy appearance tothe fibre and to fabric containing it, for example woven or knittedfabric. Dyed fabric containing fibrillated fibre tends to have a"frosted" appearance, which may be aesthetically undesirable. Suchfibrillation is believed to be caused by mechanical abrasion of thefibres during treatment in a wet and swollen state. Wet treatmentprocesses such as dyeing processes inevitably subject fibres tomechanical abrasion. Higher temperatures and longer times of treatmentgenerally tend to produce greater degrees of fibrillation. Solvent-spuncellulose fibre appears to be particularly sensitive to such abrasionand is consequently often found to be more susceptible to fibrillationthan other types of cellulose fibre. In particular, cotton has aninherently very low fibrillation tendency.

It has been known for many years to treat cellulose fibre and inparticular fabric with a crosslinking agent to improve its creaseresistance, as described for example in Kirk-Othmer's Encyclopaedia ofChemical Technology, third edition, Volume 22 (1983),Wiley-Interscience, in an article entitled "Textiles (Finishing)" atpages 769-790, and by H. Petersen in Rev. Prog. Coloration, Vol 17(1987), pages 7-22. Crosslinking agents may sometimes be referred to byother names, for example crosslinking resins, chemical finishing agentsand resin finishing agents. Crosslinking agents are small moleculescontaining a plurality of functional groups capable of reacting with thehydroxyl groups in cellulose to form crosslinks. One class ofcrosslinking agents consists of the N-methylol resins, that is to saysmall molecules containing two or more N-hydroxymethyl orN-alkoxymethyl, in particular N-methoxymethyl, groups. N-methylol resinsare generally used in conjunction with acid catalysts chosen to improvecrosslinking performance. In a typical process, a solution containingabout 5-9% by weight N-methylol resin crosslinking agent and 0.4-3.5% byweight acid catalyst is padded onto dry cellulosic fabric to give60-100% by weight wet pickup, after which the wetted fabric is dried andheated to cure and fix the crosslinking agent. In general, more than50%, often 75%, of the crosslinking agent becomes fixed to thecellulose. It is known that crease-resistant finishing treatmentsembrittle cellulose fibre and fabric with a consequent loss of abrasionresistance, tensile strength and tear strength. A balance must be struckbetween improvement in crease resistance and reduction in such othermechanical properties. It is also known that such treatments reducedyeability.

U.S. Pat. No. 4,780,102 describes a process for dyeing a smooth-drycellulosic fabric which comprises padding the cellulosic fabric with anaqueous finishing solution comprising sufficient concentrations ofN-methylol crosslinking agent, acid catalyst and polyethylene glycol(PEG) in order to impart smooth-dry and dye receptivity properties tothe fabric; drying and curing the fabric for sufficient time and atsufficient temperature to interact the components of the finish with thefabric; and dyeing the fabric with a cellulose dye. The cellulosicfabric is preferably a cotton fabric. The pad bath typically contains byweight 5-10% crosslinking agent, 0.7-0.8% zinc nitrate hexahydrate and10-20% PEG. Smooth-dry ratings begin to drop off substantially with PEGmolecular weights of 600 or less, and on this basis PEG of molecularweight 600-1450 is preferred depending on the level of smooth-dryperformance desired.

DISCLOSURE OF THE INVENTION

A method according to the present invention for reducing thefibrillation tendency of solvent-spun cellulose fibre is characterisedin that it includes the step of contacting the fibre with:

(a) a flexible linear polymer having terminal functional groups; and

(b) a crosslinking agent reactive with cellulose and with said terminalfunctional groups.

The method of the invention may be performed on never-dried fibre or onfabric, for example woven or knitted fabric, containing the fibre.Never-dried fibre is defined as fibre produced in a wet-spinningprocess, which has been coagulated and washed but which has not beendried.

The crosslinking agent may in general be any of those known in the artfor crease-resistant finishing of cellulose. The crosslinking agent ispreferably an agent classed as a low-formaldehyde or zero-formaldehydecrosslinking agent, further preferably an agent classed as azero-formaldehyde agent when the method of the invention is carried outon fabric. One class of low-formaldehyde crosslinking agents consists ofthe N-methylol resins. Examples of suitable N-methylol resins are thosedescribed in the abovementioned articles in Kirk-Othmer and by Petersen.Examples of such resins include 1,3-dimethylolethyleneurea (DMEU),1,3-dimethylolpropyleneurea (DMPU) and4,5-dihydroxy-1,3-dimethylolethyleneurea (DHDMEU). Other examplesinclude compounds based on urones, triazinones and carbamates. Anotherexample of a preferred class of crosslinking agents consists ofcompounds based on 1,3-dialkyl-4,5-dihydroxy(alkoxy)ethyleneurea, forexample 1,3-dimethyl-4,5-dihydroxyethyleneurea. A further example of asuitable crosslinking agent is melamine. Yet another example of asuitable crosslinking agent is butanetetracarboxylic acid (BTCA).

It is known that crosslinking agents for crease-resistant finishing ofcellulose are generally used in conjunction with a catalyst, commonly anacid catalyst. The method of the invention preferably utilises such acatalyst when recommended for use with the chosen crosslinking agent.For example, N-methylol resins and1,3-dialkyl-4,5-dihydroxy(alkoxy)ethyleneureas are preferably used inconjunction with an acid catalyst, for example an organic acid such asacetic acid or a latent acid such as an ammonium salt, amine salt ormetal salt, e.g. zinc nitrate or magnesium chloride. Mixed catalystsystems may be used.

The flexible linear polymer is preferably a wholly aliphatic polymer.The backbone of the flexible linear polymer is preferably unbranched.The flexible linear polymer preferably contains no functional groupsreactive with cellulose or with the crosslinking agent other than theterminal functional groups. The terminal functional groups arepreferably hydroxyl groups, although other types of groups such as aminogroups may also be suitable in some cases. Preferred types of flexiblelinear polymer include polymerised glycols such as polypropylene glycol(PPG) and in particular polyethylene glycol (PEG). Amine-tippedderivatives of such polymerised glycols may be used.

It will be understood that such flexible linear polymers are generallymixtures of molecules having a range of chain lengths and arecharacterised in terms of their average molecular weight and chainlength. The flexible linear polymer is capable of reacting through itsfunctional groups to provide a linear chain corresponding to the polymerbackbone, preferably containing on average about 5 to 150 atoms, morepreferably about 10 to 100 atoms, further preferably about 20 to 40atoms. A preferred example of a flexible linear polymer for use onnever-dried fibre is PEG having average molecular weight in the range100 to 2000, more preferably 200 to 1500, further preferably 300 to 600.In general, use on never-dried fibre of a flexible linear polymer with abackbone shorter than about 5 atoms imparts good fibrillation resistancebut an unacceptable reduction in dyeability, whereas use of a flexiblelinear polymer with a backbone longer than about 150 atoms impartslittle reduction in dyeability but only a small improvement infibrillation resistance. A preferred example of a flexible linearpolymer for use on fabric is PEG having average molecular weight in therange 300 to 400. It has been found that fabrics treated with PEG ofthis molecular weight range exhibit good resistance to fibrillation andgood dyeability, whereas fabrics treated with PEG of molecular weightoutside this range may possess good resistance to fibrillation but ingeneral exhibit reduced dyeability.

The crosslinking agent, flexible linear polymer and any catalyst arepreferably contacted with the fibre from solution, preferably an aqueoussolution. Polymerised glycols such as PEG and PPG are generally solublein water.

The solution may be applied to never-dried fibre in known types of ways,for example the solution may be padded on to the never-dried fibre orthe never-dried fibre may be passed through a treatment bath of thesolution. The never-dried fibre may have a moisture content of about45-55%, often around 50%, by weight, after contacting with the solution.Application of the solution to the never-dried fibre may be carried outin such a way that part or substantially all of the water in thenever-dried fibre is replaced by the solution. The never-dried fibre maybe in tow or staple form. The solution may contain 0.2 to 15%,preferably 0.5 to 10%, more preferably 0.5 to 5%, by weight crosslinkingagent (expressed on a 100% activity basis). The solution preferablycontains 0.5 to 5% by weight flexible linear polymer. When a catalyst isused, the solution may contain 0.1 to 5%, preferably 0.25 to 2.5%, byweight catalyst. The solution may contain one or more additionalsubstances, for example a soft finish for the fibre. It is an advantageof the method of the invention as applied to never-dried fibre that itcan be combined with another treatment step, such as the application ofsoft finish.

The treated wet never-dried fibre preferably contains 0.2 to 5%, morepreferably 0.5 to 2%, by weight crosslinking agent calculated on weightof cellulose. The treated wet never-dried fibre preferably contains 0.5to 3% by weight flexible linear polymer calculated on weight ofcellulose.

The solution may be applied to fabric in known types of ways, forexample the solution may be padded onto the fabric or the fabric may bepassed through a treatment bath of the solution. The solution maycontain 2.5 to 10%, preferably to 7.5%, by weight crosslinking agent(expressed on a 100% activity basis). The solution may contain 5 to 20%,preferably 10 to 15%, by weight flexible linear polymer. When a catalystis used the solution may contain 0.1 to 5%, preferably 0.25 to 2.5%, byweight catalyst. It has remarkably been observed that in generalclosely-defined conditions are required for fabric treatment in order toavoid reduction in dyeability of the fabric.

It has been observed that treatment of fibre in the never-dried stateaccording to the invention may give rise to roughnesses in spun yarnsprepared from the treated fibre, which may be undesirable in someapplications. Treatment of fabric according to the invention does notgive rise to surface roughnesses.

In one embodiment of the invention, the crosslinking agent and flexiblelinear polymer are utilised as separate materials. In another embodimentof the invention, the terminal functional groups in the flexible linearpolymer are first reacted with the crosslinking agent to provide aflexible linear polymer having terminal functional groups reactive withcellulose, and never-dried cellulose is subsequently treated with thislatter polymer. For example, the crosslinking agent and the flexiblelinear polymer may react together in solution before application to thefibre.

After treatment with crosslinking agent and flexible linear polymeraccording to the invention, the fibre is heated to fix and cure thecrosslinking agent and is dried. The heating step may precede, be partof or follow the drying step. When the method is applied to never-driedfibre, dry staple fibre may be converted to yarn which is then heated tocure and fix the crosslinking agent. The time and temperature requiredin the heating step depend on the nature of the crosslinking agent andoptional catalyst employed. After heating and drying, the fibre maycontain about 0.1 to 4%, preferably 0.5 to 2%, by weight fixedcrosslinking agent calculated on weight of cellulose. It has generallybeen found that about 70 to 75% of the crosslinking agent in the wetfibre may become fixed to the cellulose.

Fibre treated according to the method of the invention may subsequentlybe dyed with conventional dyes for cellulose fibres.

The method of the invention has the advantage that it may be applied tonever-dried fibre, so that protection against fibrillation can beprovided at an early stage. Never-dried fibre treated according to theinvention exhibits little reduction in dyeability compared withuntreated fibre. Fibre treated according to the invention has excellentresistance to fibrillation compared with untreated fibre. Fabric madefrom never-dried fibre treated according to the method of the invention,for example woven or knitted fabric, can be subjected to severemechanical treatment in the wet state, such as rope dyeing, withoutexcessive fibrillation. The fabric may be laundered with only little orslow loss of the reduction in fibrillation tendency. The method of theinvention generally imparts little if any improvement in creaseresistance to fabric made from fibre treated in the never-dried state,and it is remarkable that it nevertheless provides effective protectionagainst fibrillation.

Known methods for the manufacture of solvent-spun cellulose fibreinclude the steps of:

(i) dissolving cellulose in a solvent to form a solution, the solventbeing miscible with water;

(ii) extruding the solution through a die to form a fibre precursor;

(iii) passing the fibre precursor through at least one water bath toremove the solvent and form the fibre; and

(iv) drying the fibre.

The wet fibre at the end of step (iii) is never-dried fibre andtypically has a water imbibition in the range 120-150% by weight. Thedried fibre after step (iv) typically has a water imbibition of around60-80% by weight. Solvent-spun cellulose never-dried fibre is treatedaccording to the method of the invention before it has been dried, thatis to say between steps (iii) and (iv).

The invention is illustrated by the following Examples. In each case,the never-dried fibre used was prepared by extruding a solution ofcellulose in N-methylmorpholine N-oxide (NMMO) into an aqueous bath andwashing the fibre so formed with water until it was essentially free ofNMMO.

Materials were assessed for degree of fibrillation using the methoddescribed below as Test Method 1 and assessed for fibrillation tendencyusing the techniques described below as Test Methods 2A and 2B.

Test Method 1 (Assessment of Fibrillation)

There is no universally accepted standard for assessment offibrillation, and the following method was used to assess FibrillationIndex (F.I.). Samples of fibre were arranged into a series showingincreasing degrees of fibrillation. A standard length of fibre from eachsample was then measured and the number of fibrils (fine hairy spursextending from the main body of the fibre) along the standard length wascounted. The length of each fibril was measured, and an arbitrarynumber, being the product of the number of fibrils multiplied by theaverage length of each fibril, was determined for each fibre. The fibreexhibiting the highest value of this product was identified as being themost fibrillated fibre and was assigned an arbitrary Fibrillation Indexof 10. A wholly unfibrillated fibre was assigned a Fibrillation Index ofzero, and the remaining fibres were graded from 0 to 10 based on themicroscopically measured arbitrary numbers.

The measured fibres were then used to form a standard graded scale. Todetermine the Fibrillation Index for any other sample of fibre, five orten fibres were visually compared under the microscope with the standardgraded fibres. The visually determined numbers for each fibre were thenaveraged to give a Fibrillation Index for the sample under test. It willbe appreciated that visual determination and averaging is many timesquicker than measurement, and it has been found that skilled fibretechnologists are consistent in their rating of fibres.

Fibrillation Index of fabrics can be assessed on fibres drawn from thesurface of the fabric. Woven and knitted fabrics having F.I. of morethan about 2.0 to 2.5 exhibit an unsightly appearance.

Test Method 2 (Inducement of Fibrillation)

Method 2A (Blender)

0.5 g fibre cut into 5-6 mm lengths and dispersed in 500 ml water atambient temperature was placed in a household blender (liquidiser) andthe blender run for 2 minutes at about 12000 rpm. The fibre was thencollected and dried.

Method 2B (Scour Bleach, Dye)

(i) Scour

1 g fibre was placed in a stainless steel cylinder approximately 25 cmlong by 4 cm diameter and having a capacity of approximately 250 ml. 50ml conventional scouring solution containing 2 g/l Detergyl FS955 (ananionic detergent available from ICI plc) (Detergyl is a Trade Mark) and2 g/l sodium carbonate was added, a screw cap fitted and the cappedcylinder tumbled end-over-end at 60 tumbles per minute for 60 minutes at95° C. The scoured fibre was then rinsed with hot and cold water.

(ii) Bleach

50 ml bleaching solution containing 15 ml/l 35% hydrogen peroxide, 1 g/lsodium hydroxide, 2 g/l Prestogen PC (a bleach stabiliser available fromBASF AG) (Prestogen is a Trade Mark) and 0.5 ml/l Irgalon PA (asequestrant available from Ciba-Geigy AG) (Irgalon is a Trade Mark) wasadded to the fibre and a screw cap fitted to the cylinder. The cylinderwas then tumbled as before for 90 minutes at 95° C. The bleached fibrewas then rinsed with hot and cold water.

(iii) Dye

50 ml dyeing solution containing 8% on weight of fibre Procion Navy HER150 (a reactive dye) (Procion is a Trade Mark of ICI plc) and 55 g/lGlauber's salt was added and the cylinder was capped and tumbled asbefore for 10 minutes at 40° C. The temperature was raised to 80° C. andsufficient sodium carbonate added to give a concentration of 20 g/l Thecylinder was then capped once more and tumbled for 60 minutes. The fibrewas rinsed with water. 50 ml solution containing 2 ml/l Sandopur SR (adetergent available from Sandoz AG) (Sandopur is a Trade Mark) was thenadded and the cylinder capped. The cylinder was then tumbled as beforefor 20 minutes at 100° C. The dyed fibre was then rinsed and dried.

Method 2A provides more severe fibrillating conditions than Method 2B.

EXAMPLE 1

Never-dried solvent-spun cellulose fibre was immersed in a bathcontaining varying levels of 1,3-dimethyl-4,5-dihydroxyethyleneurea(available from Hoechst AG under the Trade Mark Arkofix NZF), CatalystNKD (a magnesium chloride/acetic acid catalyst available from HoechstAG) (25% by weight on Arkofix NZF), polyethylene glycol (PEG) of variousaverage molecular weights (MW), and DP3408 (a polyether/polyacrylicsystem available from Precision Processes (Textiles) of Ambergate,Derbyshire). The fibre was then dried at a temperature of 100° C.followed by curing at 170° C. for 20 seconds. The fibre was thenassessed for fibrillation tendency by Test Method 2A. Fibrillation Index(F.I.) results are shown below in Table 1A:

                                      TABLE 1A                                    __________________________________________________________________________    Arkofix   DP3408                                                                             PEG                                                                              PEG MW (top row) and FI (body of table)                     Trial                                                                              NZF g/l                                                                            g/l  g/l                                                                              200                                                                              300 400                                                                              600 1500                                                                             2000                                       __________________________________________________________________________    1    30    5   10 1.8                                                                              0.2 0.1                                                                              0.6 3.0                                                                              2.8                                        2    30   10   20 2.0                                                                              1. 5                                                                              0.1                                                                              1.3 1.1                                                                              2.4                                        3    30   20   30 3.1                                                                              1.1 0.8                                                                              0.3 2.6                                                                              2.4                                        4    50    5   20 0.7                                                                              2.1 1.7                                                                              1.7 0.4                                                                              3.2                                        5    50   10   30 0.3                                                                              1.3 1.3                                                                              1.9 1.9                                                                              2.5                                        6    50   20   10 1.9                                                                              1.3 0.5                                                                              1.7 3.3                                                                              2.0                                        7    50    5   30 1.7                                                                              0.1 0.1                                                                              1.1 0.8                                                                              0.5                                        8    80   10   10 0.1                                                                              1.4 0.6                                                                              2.1 0.3                                                                              1.7                                        9    80   20   20 1.4                                                                              0.6 0.1                                                                              0.7 1.2                                                                              2.4                                        Average           1.4                                                                              1.1 0.6                                                                              1.3 1.6                                                                              2.2                                        __________________________________________________________________________

A control sample of untreated fibre exhibited a Fibrillation Index of5.0.

Experiments which gave good values of Fibrillation Index at eachmolecular weight of PEG were repeated, and the results are shown belowin Table 1B:

                  TABLE 1B                                                        ______________________________________                                        Arkofix    DP3408   PEG       PEG                                             NZF g/l    g/l      g/l       MW    F.I.                                      ______________________________________                                        50         10       10        200   0.2                                       80         10       30        300   0.0                                       80         10       30        400   0.0                                       80         20       10        600   0.2                                       80         10       20        1500  3.0                                       80          5       30        2000  1.8                                       ______________________________________                                    

EXAMPLE 2

Never-dried solvent-spun cellulose fibre was immersed in bathscontaining varying levels of Arkofix NZF, Catalyst NED (25% by weight onArkofix NZF) and PEG of average molecular weight 300. The fibre was thendried at 100° C. and cured for 20 seconds at 170° C. Fibrillation wasinduced using Test Method 2A, or 2B, or 2B followed by 2A, and F.I. wasassessed using Test Method 1. Results are shown below in Table 2:

                  TABLE 2                                                         ______________________________________                                        Arkofix NZF  PEG 300  Fibrillation Index                                      g/l          g/l      2A      2B  2B + 2A                                     ______________________________________                                        50           10       0.0     0.9 3.3                                         30           10       0.0     1.9 3.8                                         70           30       0.6     0.4 1.6                                         Control      --       5.2     --  --                                          ______________________________________                                    

EXAMPLE 3

Never-dried solvent-spun cellulose fibre was immersed in a bathcontaining varying levels of Arkofix NZF, magnesium chloride catalyst(25% by weight on Arkofix NZF) and PEG of average molecular weight 400(30 g/l). The fibre was then dried at 100° C. and cured for 20 secondsat 170° C. Fibrillation was induced using Test Method 2A, or 2B followedby 2A, and F.I. was assessed using Test Method 1. F.I., tenacity andextensibility results are shown below in Table 3:

                  TABLE 3                                                         ______________________________________                                        Arkofix NZF                                                                             Fibrillation Index                                                                         Tenacity  Extensibility                                g/l       2A     2B + 2A   cN/tex  %                                          ______________________________________                                        30        0.0    1.8       40.1    12.4                                       50        1.2    1.6       38.8    11.7                                       70        0.0    1.4       39.9    10.4                                       90        0.0    5.4       40.6    11.1                                       110       0.0    7.2       40.1     9.9                                       Control   5.2    --        41.2    12.2                                       ______________________________________                                    

EXAMPLE 4

Never-dried solvent-spun cellulose fibre was immersed in bathscontaining varying levels of Arkofix NZF, Catalyst NKD (25% by weight onArkofix NZF) and PEG of average molecular weight 300. The fibre was thendried at 100° C. and cured for 20 seconds at 170° C. The fibre was thendyed under standard conditions and its dyeability expressed in terms ofits dye uptake as a percentage of the dye uptake of an untreated controlsample. The results shown in Table 4 were obtained:

                  TABLE 4                                                         ______________________________________                                        Arkofix NZF g/l                                                                              PEG 300 g/l                                                                              Dyeability %                                        ______________________________________                                         0              0         100                                                 70             10         91.9                                                90             30         90.4                                                70              0         60                                                  ______________________________________                                    

It will observed that dyeability was very markedly reduced in thecomparative experiment in which PEG was omitted.

EXAMPLE 5

Woven fabric of solvent-spun cellulose fibre was padded with solutionscontaining varying amounts of Arkofix NZF, varying amounts of PEG ofvarying molecular weights, and magnesium chloride as catalyst (25% byweight on Arkofix NZF). The fabrics were dried at 110° C. and thenheated at 160° C. for 30 seconds to cure the resin. The fabrics weredyed with an HE-type reactive dye, and fibrillation was assessed beforeand after laundering at 60° C. (10 wash/tumble cycles). The resultsshown in Table 5 were obtained:

                  TABLE 5                                                         ______________________________________                                        Arkofix                                                                       NZF    PEG        Dyeability                                                                              F.I.                                              g/l    M.W.    g/l    %       Unlaundered                                                                            Laundered                              ______________________________________                                         0     --       0     100     1.8      6.4                                     70    200      50    83.4    0.2      2.0                                     70    200     100    88.0    0.0      1.8                                    100    200      50    54.8    0.0      1.0                                    100    200     100    85.3    0.0      1.6                                    130    200      50    92.8    0.0      1.4                                    130    200     100    100.1   0.0      2.0                                     70    300      50    68.4    0.6      2.4                                     70    300     100    71.5    0.0      3.8                                    100    300      50    68.0    0.0      2.0                                    100    300     100    97.1    0.2      1.6                                    130    300      50    65.0    0.0      0.8                                    130    300     100    75.7    0.2      1.0                                     70    400      50    85.8    0.0      2.4                                     70    400     100    100.7   0.0      3.6                                    100    400      50    69.3    0.0      0.8                                    100    400     100    85.9    0.0      0.8                                    130    400      50    67.4    0.0      0.4                                    130    400     100    92.3    0.0      0.4                                     70    600      50    40.3    0.0      3.2                                     70    600     100    42.8    0.2      3.6                                    100    600      50    51.3    0.0      1.2                                    100    600     100    72.7    0.0      1.6                                    130    600      50    44.0    0.0      0.6                                    130    600     100    57.6    0.0      0.4                                    ______________________________________                                    

Use of low-formaldehyde resins adversely affected dyeability incomparison with the zero-formaldehyde resin used in the aboveexperiments.

EXAMPLE 6

Never-dried solvent-spun cellulose fibre was treated with an aqueoussolution containing Arkofix NZF (40 g./l ), PEG 400 (24 g/l) andmagnesium chloride (10 g/l) and dried. The treated fibre was spun intoyarn, which was knitted into a fabric. The fabric was heated at 150° C.for 1 minute to cure the resin, dyed and assessed for fibrillation afterlaundering, with the results shown in Table 6A:

                  TABLE 6A                                                        ______________________________________                                               Laundering                                                                    cycles  F.I.                                                           ______________________________________                                               0       2.0                                                                   3       1.5                                                                   5       2.5                                                                   8       3.8                                                            ______________________________________                                    

The fabric appeared hairy, as did the yarn from which it was made.Fabric hand was very soft even without the use of any softeningtreatment.

Scoured knitted fabric of solvent-spun cellulose was padded with anaqueous solution containing the zero-formaldehyde resin Quecodur FF(Trade Mark of Thor Chemicals) (160 g/l), PEG 400 (100 g/l) andmagnesium chloride (40 g/l). The treated fabric was dried and heated at150° C. for 1 minute to cure the resin. The fabric was satisfactorilydyed to medium-dark shade with reactive dyes and assessed forfibrillation after laundering, with the results shown in Table 6B:

                  TABLE 6B                                                        ______________________________________                                               Laundering                                                                    cycles  F.I.                                                           ______________________________________                                               0       0.4                                                                   3       0.8                                                                   5       1.3                                                                   8       1.1                                                            ______________________________________                                    

The fabric appeared extremely clean both before and after laundering.

I claim:
 1. A method of reducing the fibrillation tendency ofsolvent-spun cellulose fibre, which comprises contacting said fibrewith:(a) a flexible linear polymer having terminal functional groups;and (b) a crosslinking agent reactive with cellulose and with saidterminal functional groups, said flexible linear polymer containing nofunctional groups reactive with cellulose or with said crosslinkingagent other than said terminal functional groups.
 2. A method accordingto claim 1, comprising contacting said fibre with an aqueous solution ofthe flexible linear polymer and the crosslinking agent.
 3. A methodaccording to claim 1, in which the crosslinking agent is alow-formaldehyde or zero-formaldehyde crosslinking agent.
 4. A methodaccording to claim 3, comprising contacting said fibre with an acidcatalyst for the crosslinking agent.
 5. A method according to claim 1,in which the flexible linear polymer is an aliphatic polymer.
 6. Amethod according to claim 5, in which the flexible linear polymer ispolyethylene glycol.
 7. A method according to claim 1, comprisingsubsequently heating the fibre to fix and cure the crosslinking agent.8. A method according to claim 1, comprising subsequently dying thefibre.
 9. A method according to claim 1, in which the fibre isnever-dried solvent-spun cellulose fibre.
 10. A method according toclaim 9, in which the flexible linear polymer is polyethylene glycol ofaverage molecular weight in the range 300 to
 600. 11. A method accordingto claim 9 comprising contacting the fibre with an aqueous solutioncontaining 0.5 to 5 percent by weight of the crosslinking agent,expressed on a 100% activity basis.
 12. A method according to claim 9comprising contacting the fibre with an aqueous solution containing 0.5to 5 percent by weight of the flexible linear polymer.
 13. A methodaccording to claim 1, in which the fibre is present in a woven orknitted fabric.
 14. A method according to claim 13, in which theflexible linear polymer is polyethylene glycol of average molecularweight in the range 300 to
 400. 15. A method according to claim 14,comprising contacting the fabric with an aqueous solution containing 10to 15 percent by weight of the polyethylene glycol.
 16. A methodaccording to claim 13, in which the crosslinking agent is azero-formaldehyde resin.
 17. A method according to claim 13 comprisingcontacting the fabric with an aqueous solution containing 5 to 7.5percent by weight of the crosslinking agent, expressed on a 100%activity basis.